sapling #23

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Hana Sigsbee 3B
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sapling #23

Postby Hana Sigsbee 3B » Sun Nov 01, 2020 10:26 pm

The electron affinity of thulium has been measured by a technique known as laser photodetachment electron spectroscopy. In this technique, a gaseous beam of the anions of an element is bombarded with photons from a laser. Electrons from the anion are then ejected and their energies are detected. The incident radiation had a wavelength of 1064 nm, and the ejected electrons were found to have an energy of 0.137 eV. The electron affinity is the difference in energy between the incident photons and the energy of the ejected electrons. Determine the electron affinity of thulium in units of electron volts per atom.

in the problem how would I find the answer in the eV per atom?

Rachel Kho Disc 2G
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Re: sapling #23

Postby Rachel Kho Disc 2G » Sun Nov 01, 2020 10:28 pm

I'm also having trouble with this, because I got the first part of the answer correct but I don't know what I'm doing wrong for the second part. When I ask for hints, it says that I need to use conversions of eV to 1.602*10^-22 kJ, and then also Avogadro's number. Then once you have that answer, you can find the electron affinity. I think I'm doing something wrong with the conversions, though. Would someone be able to walk me through it?

Hannah Alltucker 3L
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Re: sapling #23

Postby Hannah Alltucker 3L » Sun Nov 01, 2020 10:29 pm

1 eV is 1.602 x 10^-19 Joules, so all you have to do is multiply your calculated energy!

Anil Chaganti 3L
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Re: sapling #23

Postby Anil Chaganti 3L » Sun Nov 01, 2020 10:31 pm

After calculating electron affinity using the energy of ejected electrons (convert ev to J by multiplying by 1.602 x 10^-19 J) and the energy of incident light using the wavelength (E=hc/ wavelength in m), you would get your answer in J. Then, convert this answer back to eV using the conversion factor once again (1.602 x 10^-19 J/eV). Since you are converting back to eV, you would divide by 1.602 x 10^-19 to cancel out J and get your answer in eV/mol.Then, divide by Avogadros (1 mol/6.022 x 10^23 atoms) to get your answer in eV/atom.

Valerie Tran 2B
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Re: sapling #23

Postby Valerie Tran 2B » Sun Nov 01, 2020 10:32 pm

First, you need to determine E using E = hc/wavelength (use 1064x10^-9) for wavelength. You would get 1.867x10^-19. Then you use the conversion for Joules to eV by dividing E by 1.602x10^-19 to get 1.165eV. Electron affinity is the difference between the incident radiation from the laser and the measured energy of the electrons(0.137eV). So 1.165-0.137=1.028 eV/atom

Hannah Alltucker 3L
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Joined: Wed Sep 30, 2020 9:44 pm

Re: sapling #23

Postby Hannah Alltucker 3L » Sun Nov 01, 2020 10:33 pm

For the second person on here, its asking you to convert back to kJ, and then multiply by Avogadro's number since your first answer was in eV/atoms. You can write this out like we do when converting mass to moles/etc. for other stoichiometric problems.

Joseph Hsing 2C
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Re: sapling #23

Postby Joseph Hsing 2C » Sun Nov 01, 2020 10:37 pm

Convert the given wavelength of light to energy using E=hc/lambda, then concert joules to eV with the conversion factor above has stated. After finding the difference in eV convert from eV/atom to kJ/mol!

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